1. Field of the Invention
This invention relates to an etching method for selective introduction of structures into surfaces of different substrates. A preferred embodiment refers to surface structuring of glass or glass ceramic substrates.
2. Description of Related Art
Virtually, the invention may be used everywhere, where micro and nanostructures are desired on substrate surfaces, such as in microelectronic, or where these structures are desired due to their special macroscopic appearance, such as for example for decoration purposes.
Surface structuring can be employed on a large variety of substrates in numerous fields. In particular in the field of optical use it is necessary that the surface structuring meets high demands.
Often it is the object to directly realize structures, for example in glasses or glass ceramics. Thereby, the uses are versatile and vary from the modification of glass substrates for the purpose of visual cover and the use in the field of decoration to the structuring of glass covers in photovoltaic modules or of the lower sides of glass ceramic cooktops. Currently, such products are already available on the market.
Structured substrates are produced in a large variety of ways, such as for example by rolling of the glass which is still hot or of the glass ceramic or by so-called hot pressing. In this regard, it has to be considered that micrometer and nanometer structures can only be produced in a laborious and costly way so far, partially due to the numerous changes of tools to guarantee the reproduction accuracy. Disadvantages of the methods presented here are that the structures which are produced in this way have a tendency to rounding off and that smaller structures of <50 micrometers (μm) cannot be realized or only at great expense.
Also laser methods can be used for selective removal of surface materials, but these methods result in rounding off as well, in particular in the case of sharp or steep patterns. A new development in this field also allows the production of fine structures via high energy quick-pulses. But these methods have not reached productivity and are very expensive.
With a masking of the substrate surface it is also possible to produce structures in glasses or glass ceramics via sandblasting, but the roughness of the surface depends on the graininess of the sandblasting material, i.e. the factor which determines the dimensions is the roughness. Thus, very fine regular structures cannot be produced. Masking technologies for the introduction of structures into glass and/or glass ceramics are prior art, but the dimensions of the structures to be introduced depend on the used dot mask, respectively small structures in the range of <50 μm can only be produced with great effort which is not suitable for large-scale industrial applications. In practice this results in the fact the combinations of large and small structures are not possible so far. Etching techniques which are used in mask-based microstructure technologies are wet chemical or gas phase-based etching. So for example in JP 2001188096 A, a method is described in which in this way a photosensitive glass is provided with an UV mask, subjected to UV radiation and etched subsequently.
Also etching of glass by means of HF is known, for example from DE 3122544 A, which describes a method using an etch cover for the glass substrate for X-ray photolithography.
In contrast, in JP 6331844 A wave guide structures are realized in quartz glass using gas phase etching processes, wherein the masking technology is used as well. In this field excellent results have been achieved in the field of micro structuring in the last years. But these methods are still very expensive.
Currently, methods which are merely based on wet chemical etching are already used in large-scale industrial applications, either for the conditioning of surfaces, such as for example in the case of etch polishing or leaching of surface layers, or for the selective thinning of glass substrates.
The realization of very small structures with a size of <1 μm in glass or glass ceramic substrates is a challenge until now and cannot or only partially be achieved with the above-mentioned methods.